1. Field of the Invention
This invention is directed to preparing polymers containing in the polymeric structure a residue of an optically active compound which residue can be removed from the resultant polymer whereby to provide polymers which in their physical structure have a void or cavity corresponding to the size and shape of the optically active residue removed therefrom. The polymers containing functional groups in a definite three-dimensional arrangement externally at their boundary surface are in cavities.
Such polymers can be used in the shape and size selective absorption of optically active antipodes and in specific interactions through the functional groups with those of the optically active antipodes, i.e., in the racemization of racemates into their optically active forms. This invention is also directed to the use of such new polymeric forms containing a void of size and shape corresponding to an optically active chemical compound for the racemization of racemates. This invention also includes polymers prepared with the use of a polyfunctional, achiral matrix molecule, that can be removed from the polymer, whereby to provide polymers containing functional groups in a definite three dimensional arrangement in cavities. They can be used in specific adsorption and interaction with molecules, whose residues and functional groups correspond to the size and shape of the void and to the functional groups therein. In this way it is possible to achieve separations of otherwise difficulty separable mixtures. The present invention can be considered to be directed to a method of preparing polymers which polymers can be considered to be analogous to enzymes.
2. Discussion of the Prior Art
In enzymes, which are to be considered as biopolymers, the functional groups responsible for interaction with a substrate or receptor are located at quite different points on the peptide chain of the macromolecule and are brought into spatial proximity only by the specific folding of the chain. In the transfer of information these functional groups interact with the corresponding parts of a substrate and thus produce the activity of a reaction of this substrate. Since the spatial arrangement of the peptide chain determines the proximity of the functional groups, the desired information cannot be transferred bi-dimensionally as is the case in certain hormones, but is performed tridimensionally at those points at which the functional groups in the space come into proximity.
A number of attempts have been made to produce synthetic enzyme analogs by copolymerizing a plurality of monomers containing different functional groups, thereby obtaining polymers in which the functional groups are randomly distributed in space and the proximity of two different groups occurs only on a purely fortuitous basis. This imperfect proximity relationship of the functional groups in the synthetic enzymes prepared hitherto may also be held responsible for their comparatively poor catalytic activity, so that these compounds can be evaluated as enzyme models to no more than a limited degree.
Polymers are also known which contain optically active compounds in the molecule. For example, L-lysine hydrochloride has been polycondensed with aromatic or aliphatic dicarboxylic acid chlorides to form polymers (cf. J. Pol.Sc. A-1, 9 (1971), pp. 2413 et seq.). In these polymers, however, the optically active substance is permanently built into the macromolecule and cannot be split off from it again. Furthermore, this procedure does not assure a steric, three-dimensional proximity relationship of functional groups.
The following conditions must accordingly be taken into consideration in preparing polymers analogous to enzymes:
1. The polymer must have several different functional groups. PA1 2. The functional groups must not be randomly distributed in space but must be in suitable proximity to one another. PA1 3. The proximity of the functional groups should be not only bidimensional but also tridimensional. PA1 4. The polymer obtained should be able to enter into specific interaction with substrates.
It is heretofore known that racemates can be resolved into their optically active forms. It has also been proposed heretofore to utilize polymers of optically active groups either in the main chain of the polymer or grafted onto side chains, or, in the case of acids or bases, bonded to ion exchangers by means of electrostatic interactions. These polymers have been used to resolve racemates into their opticaly active forms. The best effects which have been achieved with polymers containing grafted chiral groups. However, the resolving factor in the resolution of DL-mandelic acid on chloromethylated polystyrene grafted with optically active amines was only 1.004 (See Journal of Organic Chemistry, Vol. 31, p. 561 (1966)).
It therefore became desirable to provide an effective means for the resolution of optically active compounds utilizing polymers. More especially, it became desirable to provide a size and shape selective molecular absorbent which would preferentially interact with one optically active form of a given compound from its opposed rotatory form. For instance, it became desirable to provide a sized and shaped molecular absorbent which would preferentially absorb a dextro or levo rotatory form in preference to the other optically active form, i.e., the remaining optical isomer.